#include<iostream>
#include<vector>
#include<queue>
using namespace std;

class Solution {
    bool vis[51][51];
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
    int m, n, ret, count;
public:
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        m = grid.size(), n = grid[0].size();

        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (grid[i][j] == 1 && !vis[i][j])
                {
                    count = 0;
                    bfs(grid, i, j);
                    ret = max(ret, count);
                }
            }
        }
        return ret;
    }

    void bfs(vector<vector<int>>& grid, int i, int j)
    {
        vis[i][j] = true;
        count++;
        queue<pair<int, int>> q;
        q.push({ i,j });
        while (q.size())
        {
            int a = q.front().first;
            int b = q.front().second;
            q.pop();
            for (int k = 0; k < 4; k++)
            {
                int x = a + dx[k], y = b + dy[k];
                if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1 && !vis[x][y])
                {
                    count++;
                    q.push({ x,y });
                    vis[x][y] = true;
                }
            }
        }



        return;

    }
};